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x86: implement interrupt stack trampoline

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Upon hard/soft irq or exception entry/exit, handle transitions
off or onto the trampoline stack, which is the only stack that
can be used on the kernel side when the shadow page table
is active. We swap page tables when on this stack.

Adjustments to page tables are now as follows:

- Any adjustments for stack memory access now are always done
  to the user page tables

- Any adjustments for memory domains are now always done to
  the user page tables

- With KPTI, resetting a page now clears the present bit

Signed-off-by: Andrew Boie <andrew.p.boie@intel.com>
This commit is contained in:
Andrew Boie 2019-02-06 15:35:24 -08:00 • committed by Anas Nashif
commit 2cfeba8507
10 changed files with 275 additions and 50 deletions
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49
arch/x86/core/x86_mmu.c
View file

@ -89,7 +89,7 @@ int _arch_buffer_validate(void *addr, size_t size, int write)
}
struct x86_mmu_pd *pd_address =
X86_MMU_GET_PD_ADDR_INDEX(&z_x86_kernel_pdpt, pdpte);
X86_MMU_GET_PD_ADDR_INDEX(&USER_PDPT, pdpte);
/* Iterate for all the pde's the buffer might take up.
* (depends on the size of the buffer and start address
@ -192,6 +192,22 @@ void _x86_mmu_set_flags(struct x86_mmu_pdpt *pdpt, void *ptr,
}
#ifdef CONFIG_X86_USERSPACE
void z_x86_reset_pages(void *start, size_t size)
{
#ifdef CONFIG_X86_KPTI
/* Clear both present bit and access flags. Only applies
* to threads running in user mode.
*/
_x86_mmu_set_flags(&z_x86_user_pdpt, start, size,
MMU_ENTRY_NOT_PRESENT,
K_MEM_PARTITION_PERM_MASK | MMU_PTE_P_MASK);
#else
/* Mark as supervisor read-write, user mode no access */
_x86_mmu_set_flags(&z_x86_kernel_pdpt, start, size,
K_MEM_PARTITION_P_RW_U_NA,
K_MEM_PARTITION_PERM_MASK);
#endif /* CONFIG_X86_KPTI */
}
/* Helper macros needed to be passed to x86_update_mem_domain_pages */
#define X86_MEM_DOMAIN_SET_PAGES (0U)
@ -230,18 +246,22 @@ static inline void _x86_mem_domain_pages_update(struct k_mem_domain *mem_domain,
partitions_count++;
if (page_conf == X86_MEM_DOMAIN_SET_PAGES) {
/* Set the partition attributes */
_x86_mmu_set_flags(&z_x86_kernel_pdpt,
u64_t attr, mask;
#if CONFIG_X86_KPTI
attr = partition.attr | MMU_ENTRY_PRESENT;
mask = K_MEM_PARTITION_PERM_MASK | MMU_PTE_P_MASK;
#else
attr = partition.attr;
mask = K_MEM_PARTITION_PERM_MASK;
#endif /* CONFIG_X86_KPTI */
_x86_mmu_set_flags(&USER_PDPT,
(void *)partition.start,
partition.size,
partition.attr,
K_MEM_PARTITION_PERM_MASK);
partition.size, attr, mask);
} else {
/* Reset the pages to supervisor RW only */
_x86_mmu_set_flags(&z_x86_kernel_pdpt,
(void *)partition.start,
partition.size,
K_MEM_PARTITION_P_RW_U_NA,
K_MEM_PARTITION_PERM_MASK);
z_x86_reset_pages((void *)partition.start,
partition.size);
}
}
out:
@ -277,12 +297,7 @@ void _arch_mem_domain_partition_remove(struct k_mem_domain *domain,
"invalid partitions");
partition = domain->partitions[partition_id];
_x86_mmu_set_flags(&z_x86_kernel_pdpt, (void *)partition.start,
partition.size,
K_MEM_PARTITION_P_RW_U_NA,
K_MEM_PARTITION_PERM_MASK);
z_x86_reset_pages((void *)partition.start, partition.size);
out:
return;
}